This invention is described herein with reference to an AC gas discharge plasma display panel (PDP). However, this invention may also be practiced with other display technologies including other flat panel displays and projection displays. Both passive and matrix displays may be used including passive matrix and active matrix displays.
Such other display technologies include DC gas discharge (plasma) displays, electroluminescent displays (ELD), liquid crystal displays (LCD) including active matrix or thin film transistor LCD, passive LCD, light-emitting diode displays (LED), ferroelectric liquid crystal (FLC) displays, organic electroluminescent (OEL) displays, and organic light emitting diode (OLED) displays.
OLED is also called organic light emitting display. OLED is divided into molecular electroluminescent (EL) and polymer EL. Molecular OLED is disclosed in the prior art by Eastman Kodak, Pioneer of Japan, and Sanyo of Japan. Polymer OLED is disclosed by Philips of Holland, Dow Chemical, UNIAX, and Cambridge University (UK). OLED may be passive matrix or active matrix.
Other display technologies also include projection displays such as digital micromirror device (DMD) arrays are disclosed in the prior art by Texas Instruments. Liquid Crystal on Silicon (LCOS) displays are contemplated. This invention is especially suitable with displays which use time multiplexing gray scale.
A plasma display panel (PDP) consists of a grid of addressable cell elements, also called pixels or subpixels. As used herein, pixel means subpixel, cell, or subcell and cell means subcell, pixel, or subpixel. A cell or pixel element is defined by the cross point of a row electrode and a column electrode for a columnar discharge display or a column electrode and two row electrodes for a surface discharge display. In the case of a surface discharge display, a pair of row electrodes (X and Y) are termed scan electrode and sustain electrode. In both columnar discharge and surface discharge PDP displays, the electrode are coated with dielectric. As part of each cell element, there is an ionizable gas. When the appropriate voltages are applied to the row and column electrodes, the ionizable gas discharges. The discharge may produce visible light or UV light that excites a phosphor. In either case, the cell only has two states, a “light-emitting” state and a “non-light-emitting” state. In most applications, gray scale is achieved through time multiplexing. In a single video frame, the number of times cells are put into the discharge state is proportional to the input luminance defined by the input video signal. The input luminescence is the digitally created video input to a PDP from a video receiver or other source.
A single video field is divided in time into ‘n’ number of weighted subfields, each weighted by a unique number of discharge pulses (or sustain pulses). A subfield consists of an addressing period in which cells are selected to be “light emitting” or “non light emitting” and a sustain period in which cells that have been selected to be “light-emitting” produce light proportional to the number of sustains in the subfield. In practice the number of subfields (n) in a field is limited by various timing constraints including addressing time and sustain time. These in turn may be dependent on various physical attributes of the plasma display panel, including display structure, display resolution, gas composition, gas pressure, and the number of rows to address.